CN107623328B - Method for reducing closed loop current of power distribution network - Google Patents

Method for reducing closed loop current of power distribution network Download PDF

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CN107623328B
CN107623328B CN201710870674.0A CN201710870674A CN107623328B CN 107623328 B CN107623328 B CN 107623328B CN 201710870674 A CN201710870674 A CN 201710870674A CN 107623328 B CN107623328 B CN 107623328B
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voltage
loop
calculation
current
voltage side
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CN107623328A (en
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徐大勇
朱凌
王毕元
徐宝琦
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Huizhou Power Supply Bureau of Guangdong Power Grid Co Ltd
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Huizhou Power Supply Bureau of Guangdong Power Grid Co Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/30—Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
    • Y02B70/3225—Demand response systems, e.g. load shedding, peak shaving
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S20/00—Management or operation of end-user stationary applications or the last stages of power distribution; Controlling, monitoring or operating thereof
    • Y04S20/20—End-user application control systems
    • Y04S20/222—Demand response systems, e.g. load shedding, peak shaving

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Abstract

The invention relates to the field of power grid dispatching automation, in particular to a method for reducing closed loop current of a power distribution network, which comprises the following step S1 of splicing a main distribution network model. And S2, performing state evaluation on the spliced model. And S3, grouping the capacitive reactance devices and sorting the capacitive reactance devices according to the capacity. And S4, performing initial power flow calculation. And S5, calculating loop closing current. And S6, judging whether the calculation termination condition is met, S7, judging whether switchable capacitive reactors exist, and S8 switching the capacitive reactors one by one according to the group sequence. And S9, performing load flow calculation again. And S10, sequencing the voltage amplitude variation according to the groups and calculating the loop closing current. And S11, operating the main gear and performing load flow calculation. S12, loop closing current calculation is carried out, and S13 judges whether the calculation condition is ended or not. The invention can actively reduce the loop closing current to the switch protection limit, prevent tripping caused by overlarge loop closing current and out-of-limit, and reduce the power failure risk caused by failure of loop closing operation.

Description

Method for reducing closed loop current of power distribution network
Technical Field
The invention relates to the field of power grid dispatching automation, in particular to a method for reducing closed loop current of a power distribution network.
Background
The size and the distribution position of the load in the power distribution network influence the distribution of the voltage of the power grid, so that a certain potential difference exists between two sides of the closed-loop switch. When the loop closing operation is carried out, under the action of the potential difference, a loop current is generated in the looped network, so that the tide distribution of the power grid is changed. Therefore, the potential difference between the two sides of the loop closing switch caused by the asymmetry of the network structure and the load distribution is a main cause of the loop closing current.
When the power distribution network is subjected to maintenance and load transfer in a non-fault area, loop closing operation is often required. During loop closing, the size of loop closing current must be controlled, and the loop closing of the two lines can be performed only when the loop closing current is ensured not to exceed the protection limit, otherwise, the loop closing current is over-large and out-of-limit to trip, so that the operation is failed, and the power failure range is expanded.
For a power distribution network, the magnitude of the closed-loop current is related to factors such as voltage amplitude difference, phase angle difference and equivalent impedance on two sides of a closed-loop point, once the calculated closed-loop current exceeds a protection limit, according to an operation rule, a regulation and control worker cannot perform closed-loop operation, only passively waits for the closed-loop current to be reduced to the protection limit of a switch and then performs closed-loop operation, and when the closed-loop current cannot exceed the breaking capacity of the switch, certain uncertainty is generated, and a power failure area cannot be recovered in time.
Disclosure of Invention
The invention aims to overcome at least one defect in the prior art, and provides a method for reducing the loop closing current of a power distribution network, which can actively reduce the loop closing current to the protection limit of a switch, thereby preventing the excessive and out-of-limit tripping of the loop closing current and further preventing the expansion of the power failure range caused by operation failure.
In order to solve the technical problems, the invention adopts the technical scheme that: a method for reducing closed loop current of a power distribution network comprises the following steps:
s1, splicing the main network model and the distribution network model;
s2, performing state evaluation on the spliced model;
s3, grouping the capacitive reactance devices and sorting the capacitive reactance devices according to capacity;
s4, performing initial load flow calculation;
s5, calculating loop closing current;
s6, judging whether the calculation termination condition is met, if not, continuing to perform the next operation;
s7, judging whether a switchable capacitive reactance device exists or not;
s8, switching the capacitive reactors one by one according to the group sequence;
s9, carrying out load flow calculation again;
s10, calculating loop closing current and judging whether to terminate the calculation;
s11, when no switchable capacitive reactance exists, operating the main transformer gear and carrying out load flow calculation again;
s12, calculating loop closing current and judging whether to terminate the calculation;
s13, the calculation is terminated.
Further, in step S1, the master-distribution network model is spliced: the size of the closed loop current in the power distribution network is greatly influenced by a power grid structure, particularly by power grid subareas, the calculation of the closed loop current cannot be effectively finished only by depending on a power distribution network model, and the reliability of a calculation result is low. And splicing the main network model and the distribution network model according to a power grid hierarchical management principle.
The spliced model is a node-branch model. The following three types of models are mainly classified:
a. bus node: a bus of a switch station and a 10kV bus of a transformer substation in a power distribution network are simplified into bus nodes.
b. Branch circuit: the cable branch and the overhead line are used as branch circuits.
c. Winding: the transformer is used as a winding.
Further, in step S2, a state estimation is performed on the spliced model, and the state estimation is a basic application of power system analysis, and aims to estimate an actual operating state of the power grid according to measurement information of the power grid, and is generally performed based on a weighted least square principle in practical use.
The method comprises the steps of partitioning a measured Jacobian matrix by utilizing the partitioning characteristics of the state estimation problem of the power system, optimizing column numbers according to the partitioning sparse structure of an information matrix, adopting a variable rotating shaft column-by-column elimination strategy, dynamically selecting rotating shaft elements based on a minimum principle, and selecting rotating elements according to the principle that non-zero injected elements are the least, so that the required memory space is reduced, and the execution efficiency is obviously improved.
Further, in step S3, the capacitors, reactors, and transformers on both sides of the loop closing switch are listed, the capacitive reactance devices are sorted in groups according to the size of the capacitance, and the high voltage side capacitor, the low voltage side reactor, the low voltage side capacitor, and the high voltage side reactor are sequentially sorted.
Further, in step S4, an initial load flow calculation is performed on the switch to be closed, and a proportional difference of the bus voltage difference is obtained.
Further, in step S5, after calculating the loop closing current, if the switching loop closing current exceeds the switching protection limit, continuing the next calculation, otherwise, stopping the loop closing calculation.
In the power distribution network, the power factor is high, and the loop closing current can be regarded as a result of the combined action of the load difference and the voltage difference. For a given network frame and mode, assuming that the load difference and the loop impedance are unchanged, the loop closing current can be influenced by adjusting the voltage difference. Therefore, the calculated equivalence of the loop closing current is as follows:
Figure BDA0001414917740000021
wherein:
Iloop_basethe effective value of the closed loop current is;
Ibasethe circulating current is caused by the difference value of the loads on the two sides before the loop closing;
Figure BDA0001414917740000022
the voltage vector is the voltage vector on the side with high voltage amplitude before loop closing;
Figure BDA0001414917740000023
the voltage vector of the lower side of the voltage amplitude before loop closing is obtained.
Further, it is judged whether or not the S6 termination calculation condition is satisfied, using the calculation result of the step S5.
The termination calculation conditions include:
1, no available capacitive reactance device resource or main transformer resource exists;
2, the loop closing current is less than the protection limit;
further, if loop closing current calculation is performed due to capacitive reactance actuation, the termination condition is that no main shift resources are available.
Further, in step S7, if the calculation termination condition is not satisfied after there is no switchable capacitive reactance device, the main transformer operation S11 is performed. After there is a switchable capacitive reactance, the process proceeds to step S8 to continue.
Judging the state of capacitive reactors on two sides of the loop closing switch, and putting the capacitive reactors according to the following steps:
a. firstly, cutting off a capacitor on the side with high voltage according to the order of capacity;
b. when the side with high voltage has no switchable capacitor, switching off the reactor on the low voltage side in the order of capacity;
c. a capacitor is put into the side with low voltage;
d. when the capacitor is not connected to the low voltage side, the reactor is connected to the high voltage side.
By adopting the principles, unreasonable switching in actual operation can be avoided, the action times of the equipment are reduced, and the service life of the equipment is prolonged.
Further, in step S9, after the capacitive reactance is operated each time, the load flow calculation is performed again to obtain new amplitude values and the variation of the phase angle at both sides of the closed-loop switch;
the calculation formula is as follows:
Figure BDA0001414917740000031
wherein:
Figure BDA0001414917740000032
the voltage vector of the low-voltage side after the adjustment is obtained;
Uim-1adjusting a vector for the voltage of the low-voltage side after the last action;
Figure BDA0001414917740000033
the regulated high-voltage side voltage vector is obtained;
Figure BDA0001414917740000034
is the high-voltage side voltage vector after the last action.
Further, in step S10, the variation amounts of the voltage amplitudes of the buses after the capacitive reactance devices are switched are sorted according to the groups in step S3, and the loop closing current is recalculated until the loop closing current does not exceed the protection limit (calculation is stopped) or no capacitive reactance is movable, and calculation is stopped;
the calculation formula is as follows:
Figure BDA0001414917740000035
wherein:
Iloopis loop closing current;
ILimitfor protection quota;
Figure BDA0001414917740000036
new voltage vector after putting or cutting the capacitive reactor;
Figure BDA0001414917740000037
the voltage variation after the action is accumulated;
when the actions in the same group are completed, the next group action can be performed.
Further, in step S11, the main gears on both sides of the loop closing switch are sequentially increased and decreased according to the following calculation principle:
a. when the voltage of the high-voltage side of the main transformer corresponding to the high-voltage side is biased to the upper limit, the gear position of the high-voltage side of the corresponding main transformer is shifted upwards by one gear;
b. when the voltage of the high-voltage side of the main transformer corresponding to the voltage low side is lower than the lower limit, the gear of the high-voltage side of the corresponding main transformer is shifted downwards by one gear;
c. and after load flow calculation is carried out again, the voltage amplitude and the phase angle variation of the bus at two sides of the closed-loop switch are obtained.
The calculation formula is as follows:
Figure BDA0001414917740000041
wherein:
Figure BDA0001414917740000042
the voltage vector of the low-voltage side after the adjustment is obtained;
Uin-1adjusting a vector for the voltage of the low-voltage side after the last action;
Figure BDA0001414917740000043
the regulated high-voltage side voltage vector is obtained;
Figure BDA0001414917740000044
the vector is adjusted for the high-side voltage after the last action.
Further, in step S11, the loop closing currents are recalculated according to the formula in step S8 until the loop closing currents do not exceed the limit (stopping calculation) or are not adjustable without main gear change (stopping step S13), which is performed in sequence from large to small according to the variation amount of the bus voltage amplitude after the main gear change.
Compared with the prior art, the beneficial effects are:
1. the loop closing current can be actively reduced to the switch protection limit, so that the phenomenon that the tripping is caused by the overlarge loop closing current exceeding the limit to cause the expansion of the power failure range caused by the operation failure is prevented;
2. by adopting the principle in the step S8, unreasonable switching in actual operation can be avoided, the action times of the equipment are reduced, and the service life of the equipment is prolonged.
Drawings
FIG. 1 is a schematic flow diagram of the present invention;
fig. 2 is a flow chart of the sorting of the capacitive reactance units according to the capacity size in step S3 according to the present invention.
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the patent; for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted. The positional relationships depicted in the drawings are for illustrative purposes only and are not to be construed as limiting the present patent.
As shown in fig. 1 and 2, a method for reducing closed loop current of a power distribution network includes the following steps:
s1, splicing the main network model and the distribution network model;
s2, performing state evaluation on the spliced model;
s3, grouping the capacitive reactance devices and sorting the capacitive reactance devices according to capacity;
s4, performing initial load flow calculation;
s5, calculating loop closing current;
s6, judging whether the calculation termination condition is met, if not, continuing to perform the next operation;
s7, judging whether a switchable capacitive reactance device exists or not;
s8, switching the capacitive reactors one by one according to the group sequence;
s9, carrying out load flow calculation again;
s10, calculating loop closing current and judging whether to terminate the calculation;
s11, when no switchable capacitive reactance exists, operating the main transformer gear and carrying out load flow calculation again;
s12, calculating loop closing current and judging whether to terminate the calculation;
s13, the calculation is terminated.
In this embodiment, in step S1, the master-distribution network model is spliced: the size of the closed loop current in the power distribution network is greatly influenced by a power grid structure, particularly by power grid subareas, the calculation of the closed loop current cannot be effectively finished only by depending on a power distribution network model, and the reliability of a calculation result is low. And splicing the main network model and the distribution network model according to a power grid hierarchical management principle.
The spliced model is a node-branch model. The following three types of models are mainly classified:
a. bus node: a bus of a switch station and a 10kV bus of a transformer substation in a power distribution network are simplified into bus nodes.
b. Branch circuit: the cable branch and the overhead line are used as branch circuits.
c. Winding: the transformer is used as a winding.
In this embodiment, in step S2, a state estimation is performed on the spliced model, where the state estimation is a basic application of power system analysis, and aims to estimate an actual operating state of the power grid according to measurement information of the power grid, and the state estimation is generally performed based on a weighted least square principle in practical use.
The method comprises the steps of partitioning a measured Jacobian matrix by utilizing the partitioning characteristics of the state estimation problem of the power system, optimizing column numbers according to the partitioning sparse structure of an information matrix, adopting a variable rotating shaft column-by-column elimination strategy, dynamically selecting rotating shaft elements based on a minimum principle, and selecting rotating elements according to the principle that non-zero injection elements are the least, so that the required memory space is reduced, and the execution efficiency is obviously improved.
In this embodiment, in step S3, capacitors, reactors, and transformers on both sides of the loop closing switch are listed, and the capacitive reactors are sorted in groups according to the size of the capacitance, and the high-voltage-side capacitor, the low-voltage-side reactor, the low-voltage-side capacitor, and the high-voltage-side reactor are sequentially sorted.
In this embodiment, in step S4, an initial power flow calculation is first performed on the switch to be closed, and a proportional difference of the bus voltage difference is obtained.
In this embodiment, in step S5, loop closing current is calculated, and if the switching loop closing current exceeds the switching protection limit, the next calculation is continued, otherwise, the loop closing calculation is stopped.
In the power distribution network, the power factor is high, and the loop closing current can be regarded as a result of the combined action of the load difference and the voltage difference. For a given network frame and mode, assuming that the load difference and the loop impedance are unchanged, the loop closing current can be influenced by adjusting the voltage difference. Therefore, the calculated equivalence of the loop closing current is as follows:
Figure BDA0001414917740000051
wherein:
Iloop_basethe effective value of the closed loop current is;
Ibasethe circulating current is caused by the difference value of the loads on the two sides before the loop closing;
Figure BDA0001414917740000061
the voltage vector of the high side of the voltage amplitude before loop closing is obtained;
Figure BDA0001414917740000062
is the voltage vector at the low side of the voltage amplitude before loop closing.
In this embodiment, in step S6, if the switching loop closing current exceeds the switching protection limit, the next step S7 is performed, otherwise, the loop closing calculation is stopped.
In this embodiment, step S7 determines whether there is a switchable capacitive reactance device, and if there is no switchable capacitive reactance device, that is, all capacitive reactance device resources are already involved in the calculation, step S11 is performed to calculate. Otherwise, the processing proceeds to step S8,
in this embodiment, in step S8, the state of the capacitive reactance devices on both sides of the loop closing switch is determined, and the capacitive reactance devices are put into operation according to the following steps:
a. firstly, cutting off a capacitor on the side with high voltage according to the order of capacity;
b. when the side with high voltage has no switchable capacitor, switching off the reactor on the low voltage side in the order of capacity;
c. a capacitor is put into the side with low voltage;
d. when the capacitor is not connected to the low voltage side, the reactor is connected to the high voltage side.
By adopting the principles, unreasonable switching in actual operation can be avoided, the action times of the equipment are reduced, and the service life of the equipment is prolonged.
In this embodiment, in step S8, after each capacitive reactance operation, the load flow calculation is performed again in S9 to obtain new amplitude values and phase angle variation values at both sides of the closed-loop switch;
the calculation formula is as follows:
Figure BDA0001414917740000063
wherein:
Figure BDA0001414917740000064
the voltage vector of the low-voltage side after the adjustment is obtained;
Uim-1adjusting a vector for the voltage of the low-voltage side after the last action;
Figure BDA0001414917740000065
the regulated high-voltage side voltage vector is obtained;
Figure BDA0001414917740000066
is the high-voltage side voltage vector after the last action.
In this embodiment, in step S10, the variation amounts of the amplitude of the bus voltage after the capacitive reactance device is switched are sorted according to the groups in step S3, and the loop closing current is recalculated until the loop closing current does not exceed the protection limit (calculation is stopped) or no capacitive reactance is movable, and calculation is stopped;
the calculation formula is as follows:
Figure BDA0001414917740000071
wherein:
Iloopis loop closing current;
ILimitfor protection quota;
Figure BDA0001414917740000072
new voltage vector after putting or cutting the capacitive reactor;
Figure BDA0001414917740000073
the voltage variation after the action is accumulated;
when the actions in the same group are completed, the next group action can be performed.
In this embodiment, in step S11, the main gears on both sides of the loop closing switch are sequentially increased and decreased, and the calculation principle is as follows:
a. when the voltage of the high-voltage side of the main transformer corresponding to the high-voltage side is biased to the upper limit, the gear position of the high-voltage side of the corresponding main transformer is shifted upwards by one gear;
b. when the voltage of the high-voltage side of the main transformer corresponding to the voltage low side is lower than the lower limit, the gear of the high-voltage side of the corresponding main transformer is shifted downwards by one gear;
c. and after load flow calculation is carried out again, the voltage amplitude and the phase angle variation of the bus at two sides of the closed-loop switch are obtained.
The calculation formula is as follows:
Figure BDA0001414917740000074
wherein:
Figure BDA0001414917740000075
the voltage vector of the low-voltage side after the adjustment is obtained;
Uin-1adjusting a vector for the voltage of the low-voltage side after the last action;
Figure BDA0001414917740000076
after this adjustmentA high side voltage vector;
Figure BDA0001414917740000077
the vector is adjusted for the high-side voltage after the last action.
In the present embodiment, in step S11, the main gear shift post-bus voltage amplitude variation is sequentially operated from large to small, the loop closing current S12 is recalculated by using the formula in step S10, and it is determined whether the condition for terminating calculation is satisfied, S6, and if so, the calculation is terminated S13.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (9)

1. A method for reducing closed loop current of a power distribution network is characterized by comprising the following steps:
s1, splicing the main network model and the distribution network model;
s2, performing state evaluation on the spliced model;
s3, grouping the capacitive reactance devices and sorting the capacitive reactance devices according to capacity;
s4, performing initial load flow calculation;
s5, calculating loop closing current;
s6, judging whether the calculation termination condition is met, if not, continuing to perform the next operation;
s7, judging whether a switchable capacitive reactance device exists or not;
s8, switching the capacitive reactors one by one according to the group sequence;
s9, carrying out load flow calculation again;
s10, calculating loop closing current and judging whether to terminate the calculation;
s11, when no switchable capacitive reactance exists, operating the main transformer gear and carrying out load flow calculation again;
s12, calculating loop closing current and judging whether to terminate the calculation;
s13, terminating the calculation;
in step S5, if the switching loop closing current exceeds the switching protection limit, continuing the next calculation, otherwise, stopping the loop closing calculation, and the calculated equivalence of the loop closing current is:
Figure FDA0002741879920000011
wherein:
Iloop_basethe effective value of the closed loop current is;
Ibasethe circulating current is caused by the difference value of the loads on the two sides before the loop closing; k is the loop admittance;
Figure FDA0002741879920000012
the voltage vector on one side of the high voltage amplitude value before loop closing;
Figure FDA0002741879920000013
the voltage vector on one side of the low voltage amplitude value before loop closing;
in step S8, the capacitive reactor is put in according to the following steps:
a. firstly, cutting off a capacitor on one side of a high voltage according to the order of the capacity;
b. when the high-voltage side has no switchable capacitor, the reactor is switched off on the low-voltage side according to the order of the capacity;
c. putting a capacitor at a low voltage side;
d. when the low voltage side is not provided with a capacitor, a reactor is put into the high voltage side.
2. The method for reducing the closed-loop current of the power distribution network according to claim 1, wherein in step S1, the main network model is spliced according to a power grid hierarchical management principle, and the spliced model is a node-branch model and mainly includes the following three types:
a. bus node: simplifying a switching station bus and a 10kV transformer substation bus in a power distribution network into bus nodes;
b. branch circuit: taking a cable branch and an overhead line as branches;
c. winding: the transformer is used as a winding.
3. The method for reducing closed-loop current of the power distribution network according to claim 1, wherein in step S2, the state estimation is performed on the spliced model, the blocking feature of the power system state estimation problem is used to block the measured jacobian matrix, the column numbering is optimized according to the blocking sparse structure of the information matrix, a variable rotating shaft column-by-column elimination strategy is adopted, rotating shaft elements are dynamically selected based on a minimum principle, and rotating elements are selected based on a principle that non-zero injected elements are the least.
4. The method for reducing closed loop current of power distribution network according to claim 1, wherein in step S3, the capacitors, reactors and transformers on both sides of the closed loop switch are listed, and the capacitive reactors are sorted by capacity size group, and the sorting is as follows: the high-voltage side capacitor, the low-voltage side reactor, the low-voltage side capacitor, and the high-voltage side reactor are sequentially arranged.
5. The method for reducing closed loop current of power distribution network of claim 1, wherein in step S6, the terminating condition comprises:
1. no available capacitive reactance device resource or main transformer resource exists;
2. the loop closing current is less than the protection limit.
6. The method for reducing closed-loop current of power distribution network of claim 1, wherein in step S9, after each capacitive reactance operation, the load flow calculation is performed again to obtain new amplitude and phase angle variation at two sides of the closed-loop switch;
the calculation formula is as follows:
Figure FDA0002741879920000031
wherein:
Figure FDA0002741879920000032
the voltage vector of the low-voltage side after the adjustment is obtained;
Uim-1adjusting a vector for the voltage of the low-voltage side after the last action;
Figure FDA0002741879920000033
the regulated high-voltage side voltage vector is obtained;
Figure FDA0002741879920000034
is the high-voltage side voltage vector after the last action.
7. The method for reducing the closed-loop current of the power distribution network according to claim 1, wherein in step S10, the variation amounts of the voltage amplitudes of the buses after the capacitive reactance device switching operation are respectively sorted according to the groups in step S3, and the closed-loop current is recalculated until the condition for stopping calculation is satisfied, and the calculation is stopped;
the calculation formula is as follows:
Figure FDA0002741879920000035
wherein:
Iloopis loop closing current;
ILimitfor protection quota;
Figure FDA0002741879920000036
new voltage vector after putting or cutting the capacitive reactor;
Figure FDA0002741879920000037
the voltage variation after the action is accumulated;
when the actions in the same group are completed, the next group action can be performed.
8. The method for reducing closed loop current of power distribution network of claim 1, wherein in step S11, the main gears on both sides of the closed loop switch are sequentially increased and decreased according to the following principle:
a. when the voltage of the high-voltage side of the main transformer corresponding to the higher voltage side is biased to the upper limit, the gear position of the high-voltage side of the corresponding main transformer is shifted upwards by one gear;
b. when the voltage of the high-voltage side of the main transformer corresponding to the low-voltage side is lower than the lower limit, the gear position of the high-voltage side of the main transformer corresponding to the low-voltage side is shifted downwards by one gear;
c. after load flow calculation is carried out again, the amplitude value and the variable quantity of a phase angle of the bus voltage at two sides of the closed-loop switch are obtained;
the calculation formula is as follows:
Figure FDA0002741879920000041
wherein:
Figure FDA0002741879920000042
the voltage vector of the low-voltage side after the adjustment is obtained;
Uin-1adjusting a vector for the voltage of the low-voltage side after the last action;
Figure FDA0002741879920000043
the regulated high-voltage side voltage vector is obtained;
Figure FDA0002741879920000044
the vector is adjusted for the high-side voltage after the last action.
9. The method for reducing the closed loop current of the power distribution network according to any one of the claims 1 to 8, wherein in step S11, the operation is performed sequentially from large to small according to the variation of the bus voltage amplitude after the main gear action, and the closed loop current is recalculated by using the formula in step S8 until the termination calculation condition is satisfied.
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